The cooling trend that continued during the Middle and Late Eocene was associated with the extension of tropical taxa into North Africa (Janis, 1993, Figure 3), which at this time was closer to the equator (Guiraud et al., 2005). Pollen analyses reveal that starting at about 45 Ma, the forest vegetation near the Gulf of Guinea presented numerous similarities with the modern tropical flora (Salard-Cheboldaeff, 1981; Maley, 1996). Recent molecular genetical studies have clearly shown that part of the equatorial forest arboreal vegetation is derived from the drier “boreo-tropical” flora which migrated towards the equator at the end of the Eocene (Schrire et al., 2005; Burgoyne et al., 2005). Conversely, other equatorial forest species appear to have evolved around the beginning of the Tertiary from an archaic Gondwanan flora (Maley, 1996; Couvreur et al., 2008).